I. Field
The following description relates generally to wireless communications, and more particularly to transmitting uplink control information multiplexed with data on multiple layers in wireless communication.
II. Relevant Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and the reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system.
A wireless communication system may include a number of base stations that can support communication for a number of user equipments (UEs). A base station may include multiple transmit and/or receive antennas. Each UE may include multiple transmit and/or receive antennas. The UEs may transmit uplink control information (UCI) on a physical uplink control channel (PUCCH). However, if UCI needs to be fed back when there is concurrent physical uplink shared channel (PUSCH) transmission, and there is only a single layer for uplink, the UCI may be multiplexed with data and sent in PUSCH in order to maintain the single-carrier waveform in the uplink.
A MIMO system employs multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas may be decomposed into NS independent channels, which are also referred to as spatial channels, where NS≦min{NT, NR}. Each of the NS independent channels corresponds to a dimension. The MIMO system can provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized. For example, multiple spatial layers may deliver multiple data streams on a given frequency-time resource. The streams may be transmitted independently on separate antennas. Thus, in order to benefit from the improved performance of a MIMO system, there may be a need for multiplexing UCI with data in PUSCH when there are multiple spatial layers for the uplink.